Image capturing devices include cameras, portable handheld electronic devices, and electronic devices. These image capturing devices can use an automatic focus mechanism to automatically adjust focus settings. Automatic focus (hereinafter also referred to as “autofocus” or “AF”) is a feature of some optical systems that allows them to obtain and in some systems to also continuously maintain correct focus on a subject, instead of requiring the operator to adjust focus manually. Automatic focus often uses a computer to run a miniature motor that focuses the lens for you. Focusing is the moving of the lens in and out until the sharpest possible image of the subject is projected onto the film or other image sensor. Depending on the distance of the subject from the camera, the lens has to be a certain distance from the film to form a clear image.
A conventional camera automatically focuses on the center of a display (e.g., viewfinder) or automatically selects a region of the display to focus (e.g., identifying faces using face detection algorithms). Alternatively, the camera overlays several focal boxes on a preview display through which a user can cycle and select, for example, with a half-press of button (e.g., nine overlaid boxes in SLR cameras). To focus on a target subject, a user also may center a focal region on a random subject, hold the focus, and subsequently move the camera so that the focal region is centered at the target subject.